Add additional top-level svn directories to the post-commit web UI.
Review Request #6828 — Created Jan. 23, 2015 and submitted
If people have a standard-layout repository with some additional top-level
directories, those additional directories would not be selectable in the
New Review Request page. I've updated our logic so that we'll treat trunk and
branches specially, and then add any additional top-level directories at the
(changes to reviewboard/scmtools/testdata/ excluded here).
Ran unit tests.